CCL25/CCR9-induced M2 macrophage polarization promotes lung cancer progression via TGF-β1-mediated activation of the JAK/STAT-PIM2 signaling pathway.

Lung cancer (LC) is a leading cause of cancer-related mortality worldwide. While the chemokine CCL25 is implicated in the tumor microenvironment, its specific role in LC is not fully understood. Here, we identify CCL25 as a key promoter of tumor progression through a novel macrophage-mediated signaling axis. Bioinformatics and clinical analyses revealed that CCL25 is highly expressed in LC and correlates with M2 macrophage infiltration and poorer patient survival. In vitro, tumor-derived CCL25 drove M2 polarization of macrophages by upregulating its receptor CCR9. Functionally, these CCL25-CCR9-induced M2 macrophages secreted TGF-β1 and significantly enhanced the proliferation, migration, and invasion of LC cells. Mechanistically, this effect was mediated through the activation of the JAK/STAT signaling pathway and the subsequent upregulation of the downstream oncogene PIM2 in tumor cells. Both pharmacological inhibition of JAK/STAT and genetic knockdown of PIM2 reversed the tumor-promoting crosstalk. Single-cell transcriptomics confirmed the presence of a TGF-β1-expressing CCR9+ M2 macrophage subset in human tumors and revealed co-expression of CCR9 and PIM2 in tumor cells. In vivo, CCL25 overexpression accelerated tumor growth and M2 macrophage infiltration. Collectively, our findings define a complete CCL25-CCR9-TGF-β1-JAK/STAT-PIM2 signaling circuit wherein tumor cells educate macrophages to, in turn, fuel their own malignant progression, highlighting this axis as a potential therapeutic target in lung cancer.